Control systems for controlling combustion events in an internal combustion engine system are known in the art. Conventional control systems are designed to control the contents within an engine's combustion cylinders or chambers (e.g., air) and the injected fuel to provide a desired trade-off between performance, noise, fuel economy, and emissions. As shown in FIG. 1, a conventional internal combustion engine system 10 includes an internal combustion engine 20 and an electronic control unit 30 for controlling operation of the engine and the various sub-systems of the engine system. The engine system 10 also includes an air path system 40 and a fuel delivery system 50 each coupled to the engine 20. The air path system 40 is operable to supply air and recycled exhaust gas to the engine's combustion cylinders. The fuel system 50 is operable to supply fuel to the engine's combustion cylinders. The fuel in the combustion cylinders is combusted in the presence of the air and recycled exhaust gas to generate the energy necessary for powering the engine. The amount of power produced by the engine 10 is primarily controlled by input from a driver 60 in the form of a torque request via the accelerator pedal of the vehicle.
The torque request is communicated to the ECU 30, which processes the torque request, and issues air actuator commands and fueling commands responsive to the torque request. The air path system 40 is actuated to add air and residual gas to the engine 20 in accordance with the air actuator commands, and the fuel system 50 adds fuel to the engine in accordance with the fueling commands. The ECU 30 includes various modules configured to determine air actuator commands and fueling commands that satisfy the torque request in view of the above-discussed trade-offs and other factors. As shown, the ECU 30 includes a supervisory controller 32 that determines and communicates a current or desired engine control state to a system properties control module 34 of the ECU. Based on the torque request from the driver 60, the engine control state, and the speed of the engine, the system properties control module 34 issues air path targets and fueling commands. The air path targets are transmitted to and received by an air path controller 36, which issues the air actuator commands to achieve the air path targets in view of performance feedback from the air path system 40. The fueling commands are transmitted to and received by the fuel system 50, which is actuated to deliver fuel to the engine to achieve the fueling amount commanded by the fueling commands.
Although the engine system 10 provides several benefits, the system also suffers from several shortcomings. The system properties control module 34 of the system 10 utilizes a feed-forward approach to separately determining the air path requests and fueling commands. Accordingly, once the air path requests and fueling commands are issued by the module 34, neither the air path requests or fueling commands are modified in response to the actual conditions realized by the fuel delivery and air delivery systems, respectively, except under abnormal operating conditions, such as reducing fuel mass to reduce particulate matter emissions. This leads to a number of undesirable behaviors. Decoupling the air path requests and fueling commands in this manner leaves the system open to reduced performance due to inherent delays in the system. Such decoupling also does not account for changes in the engine or power plant behavior over time when attempting to realize the fuel commands and air request. Additionally, prior art control representations do not properly, accurately, or efficiently account for different modes of operation resulting from various conditions, such altitude or exhaust thermal management. To account for these conditions, some systems includes a large number of two-dimensional feed-forward air path and fueling maps each accounting for one or more off-nominal considerations. Further, some systems rely solely on air path systems to attempt to correct variability and inconsistencies through a feedback mechanism of the air path system without adjusting the fueling parameters in any way.
While utilizing a large number of two-dimensional feed-forward maps may accommodate many off-nominal considerations (e.g., engine control states), the use of multiple maps cannot adequately account for all of the off-nominal considerations or conditions encountered during operation of an engine. Moreover, the more maps required for operation of an engine, the more complex the tuning and calibration process for obtaining the proper values that populate the maps. Additionally, the more maps required for operation, the more complex the control structure and hardware requirements, and the higher the burden on the engine system's ECU.
Another potential setback with conventional engine systems for controlling combustion events is the disparity in response times between the air path system and the fuel delivery system. Especially during transient operating conditions, the response time of the air path system may lag that of the fuel delivery system. However, conventional engine systems do not adequately take into account the different response times of the air path system and fuel delivery system. In other words, with conventional engine systems, the setpoints or targets for the air path system and fuel delivery system are typically set at the same time with a feed-forward approach, but the fuel delivery system setpoints are not adjusted for subsequent delays in the response time of the air path system. These fuel commands may be adjusted in an ad hoc fashion, however, it is not done in a unified way.